Dengue fever - recent outbreaks around the world

Brazil has recently experienced its worst-ever epidemic of dengue fever with about 200,000 cases and 142 deaths by the end of June 2008.

Another large outbreak occurred this year in the popular destination of the Maldives, with about 600 cases.

Significant outbreaks have also affected India, the Philippines, Thailand, Malaysia, Vietnam (20,000 cases with 20 deaths), and Indonesia, and outbreaks have also occurred in Saudi Arabia and Yemen.

Indian authors have recently described the features in nearly 400 serologically confirmed cases1. All reported fever for an average of 5 days.

There were 20 deaths (5%). Myalgia occurred in two-thirds, headache in half, abdominal pain and arthralgia in a quarter, vomiting in 16% and diarrhoea in 6%.

Encephalopathic features were uncommon, occurring in about 2%. Enlarged liver occurred in 16%, and spleen in 12%, while bleeding manifestations with thrombocytopaenia were very common, found in two-thirds.

Thrombocytopaenia (platelets <100x109/l) was present in 87%, <50x109/l in a half, and < 20x109/l in 6%. Leucopenia was also common (16%). Elevation of liver enzymes was documented in about a half of patients.

Dengue fever has 4 serotypes and sequential infection with a new serotype can occur, with increased morbidity and mortality. This study describes a DENV-3 epidemic in a population that may have previously been exposed to another serotype.

The illness range might be different in returning travellers, in whom mortality is lower, but there is high congruence between the range of laboratory abnormalities reported from India and the abnormities seen in returning travellers in the UK.

A recent case in Edinburgh, acquired in Thailand, recorded profoundly abnormal haematology within 4 days of admission.